1. Field of the Invention
The invention relates to a device mounting board and a semiconductor apparatus using the same.
2. Description of the Related Art
Portable electronics equipment including cellular phones, PDAs, DVCs, and DSCs has been advancing at increasingly fast speed. Under the circumstances, miniaturization and weight saving have become essential in order for these products to be accepted in the market. For the sake of achieving this, system LSIs of higher integration have been sought after. Meanwhile, enhanced usability and convenience have been desired of such electronics equipment, and functional and performance sophistication has been required of the LSIs to be used for the equipment. Consequently, while the LSI chips of higher integration have grown in the numbers of I/Os, miniaturization has been highly required of the packages themselves. For the sake of satisfying both the requirements, there has been a strong demand to develop a semiconductor package suited to packaging semiconductor parts on a board at a higher density. To meet this demand, various types of packaging technologies called CSP (Chip Size Package) have been developed.
Among the known examples of such packages is a BGA (Ball Grid Array). In the BGA, semiconductor chips are mounted on the packaging board and molded with a resin before solder balls are formed over an area on the other side of the board as external terminals. Since the BGA achieves the mounting area on a plane, it is relatively easy to miniaturize the package. Besides, the circuit board need not be rendered in narrower pitches, which eliminates the need for high-precision mounting technologies. The BGA can thus be used to reduce the total packaging cost even when the package itself costs relatively high.
FIG. 12 is a diagram showing the general configuration of a typical BGA. The BGA 100 is configured so that an LSI chip 102 is mounted on a glass epoxy board 106 via an adhesive layer 108. The LSI chip 102 is molded with a sealing resin 110. The LSI chip 102 and the glass epoxy board 106 are electrically connected with metal wires 104. Solder balls 112 are arranged in an array on the backside of the glass epoxy board 106. Through these solder balls 112, the BGA 100 is mounted on a printed wiring board.
Another example of CSP appears in Japanese Patent Laid-Open Publication No. 2002-94247. This publication has disclosed a system-in-package for a high-frequency LSI to be mounted on. This package comprises a base board, or a core board having a multilayer wiring structure formed thereon. Semiconductor devices including a high-frequency LSI are formed on the base board. The multilayer wiring structure is a laminated structure of the core board, a copper foil accompanied with an insulating resin layer, and the like.
The conventional technology described in the foregoing publication, however, has been susceptible to the following improvement. That is, when such a device mounting board as the base board described above includes a multilayer insulating film, the individual insulating resin layers in the multilayer insulating film may have different thicknesses, different coefficients of thermal expansion, etc. Then, the insulating resin layers in the multilayer insulating film can differ from each other in the degree of expansion and contraction due to heat cycles or the like when the semiconductor apparatus is under fabrication or in use.
As a result, there can occur a drop in adhesiveness between the insulating resin layers of the multilayer insulating film, or exfoliation of the layers. In other cases, the device mounting board can cause warpage, which might deteriorate the position accuracy and cause a drop in yield when semiconductor devices are connected by such connection methods as flip-chip and wire-bonding. Moreover, in conventional device mounting boards, the insulating layers must have large thicknesses for the sake of solving the warpage and other problems. It has thus been difficult to reduce the thicknesses and sizes of the device mounting boards.